Neutrino spin-flavour precession in magnetized white dwarf

Abstract

Due to notoriously small value of the neutrino magnetic moment, the phenomena of neutrino spin flavour precession (SFP) require a very high magnetic field. This makes only a handful of systems suitable to study this phenomenon. By the observation of SFP, the Dirac and Majorana nature of neutrinos is expected to be distinguished. In this work, we point out the potential of the white dwarf (WD) system in studying the spin-flavour oscillation of neutrinos. From recent analysis, it has been found that young isolated WDs may harbour very strong internal magnetic field, even without exhibiting any surface magnetic field. The presence of a magnetic field enhances the cooling process and along with that, renders the spin-flavour oscillation of neutrinos emitted in the neutrino cooling process. Employing the standard WD specifications, we analyse whether a magnetized WD is a suitable environment to distinguish between the Dirac and Majorana nature of the neutrino. Higher value of spin flavour transition probability implies reduced active neutrino flux which is possible to be estimated in terrestrial neutrino detectors. We find that for the current upper bound on the neutrino magnetic moment, the spin flavour transition probability of Dirac neutrinos is much higher in comparison to the Majorana neutrino which converts the active neutrino flavours to sterile in a significant amount. We also examine the sensitivity of the spin flavour transition probability to the neutrino magnetic moment.